fix(remote-externalities): child trie not loaded (#14365)

* fix remote-ext chlid keys

* sanity check test that child trie is loaded

substrate/utils/frame/remote-externalities/src/lib.rs

@@ -541,7 +541,6 @@ where
 			.rpc_get_keys_paged(prefix.clone(), at)
 			.await?
 			.into_iter()
-			.filter(|k| !is_default_child_storage_key(&k.0))
 			.collect::<Vec<_>>();
 		sp.stop_with_message(format!(
 			"✅ Found {} keys ({:.2}s)",
@@ -609,7 +608,14 @@ where
 
 		let mut sp = Spinner::with_timer(Spinners::Dots, "Inserting keys into DB...".into());
 		let start = Instant::now();
-		pending_ext.batch_insert(key_values.clone().into_iter().map(|(k, v)| (k.0, v.0)));
+		pending_ext.batch_insert(key_values.clone().into_iter().filter_map(|(k, v)| {
+			// Don't insert the child keys here, they need to be inserted seperately with all their
+			// data in the load_child_remote function.
+			match is_default_child_storage_key(&k.0) {
+				true => None,
+				false => Some((k.0, v.0)),
+			}
+		}));
 		sp.stop_with_message(format!(
 			"✅ Inserted keys into DB ({:.2}s)",
 			start.elapsed().as_secs_f32()
@@ -727,6 +733,10 @@ where
 			.collect::<Vec<_>>();
 
 		if child_roots.is_empty() {
+			info!(
+				target: LOG_TARGET,
+				"👩‍👦 no child roots found to scrape",
+			);
 			return Ok(Default::default())
 		}
 
@@ -1190,6 +1200,42 @@ mod remote_tests {
 		assert_eq!(ext.block_hash, cached_ext.block_hash);
 	}
 
+	#[tokio::test]
+	async fn child_keys_are_loaded() {
+		const CACHE: &'static str = "snapshot_retains_storage";
+		init_logger();
+
+		// create an ext with children keys
+		let child_ext = Builder::<Block>::new()
+			.mode(Mode::Online(OnlineConfig {
+				pallets: vec!["Proxy".to_owned()],
+				child_trie: true,
+				state_snapshot: Some(SnapshotConfig::new(CACHE)),
+				..Default::default()
+			}))
+			.build()
+			.await
+			.unwrap();
+
+		// create an ext without children keys
+		let ext = Builder::<Block>::new()
+			.mode(Mode::Online(OnlineConfig {
+				pallets: vec!["Proxy".to_owned()],
+				child_trie: false,
+				state_snapshot: Some(SnapshotConfig::new(CACHE)),
+				..Default::default()
+			}))
+			.build()
+			.await
+			.unwrap();
+
+		// there should be more keys in the child ext.
+		assert!(
+			child_ext.as_backend().backend_storage().keys().len() >
+				ext.as_backend().backend_storage().keys().len()
+		);
+	}
+
 	#[tokio::test]
 	async fn offline_else_online_works() {
 		const CACHE: &'static str = "offline_else_online_works_data";